ARKit : Lighting and Materials Part I

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The following tutorial aims to cover SCNLight’s, how to add them and what basic attributes are and what they signify.

Recommended Reading

The following post is based on the following documentation:

• SCNLight
• SCNMaterial

Outline

ARKit creates lighting models from two sources:

• Default lighting (Standard SceneKit Lighting)
• SCNLight Objects

Therefore, any custom lighting you may want to add to your scene must be composed of one or more ‘SCNLight’ objects.

To add SCNLights to the world, you must first create them and then add them to a SCNNode — which will represent it’s position in space. The code looks something like this

var aLight:SCNLight = SCNLight();
// Set your SCNLight attributes here
var aLightNode:SCNNode = SCNNode();
aLightNode.light = alight;
aLightNode.position = SCNVector3.init(X,Y,Z);
// Any other things you may want to do
node.addchild(aLightNode);

This light then interacts with you SCNMaterial to create dynamic, real-world lighting.

SCNLight Basic Attributes: Light Types

SCNLight’s carry the possibility to be one of many types. These are best demonstrated by the visual provided by Apple below.

So, in plain english, what do these types mean?

Ambient

A light that illuminates all objects in the scene from all directions.

Directional

A light source with a uniform direction and constant intensity.

Omni

An omnidirectional light, also known as a point light.

Spot

A light source that illuminates a cone-shaped area.

Here’s sample code as to how to set the type.

var aLight:SCNLight = SCNLight();
aLight.type = .omni // my favourite

Cool but how can I change the strength and color?

SCNLight Basic Attributes: Color

One of two ways to set the “color” of the light is via the color attribute, this takes in any UIColor and can be coded as below

var aLight:SCNLight = SCNLight();
aLight.color = UIColor.init(red:R, green:G, blue:B, alpha:1);

SCNLight Basic Attributes: Temperature

The other way that you can set the color of the light is via the temperature attribute, which is more representative of photography lighting and is measured in Kelvin.

var aLight:SCNLight = SCNLight();
aLight.temperature = 7800; // That Scandinavian blue

SCNLight Basic Attributes: Intensity

Finally, the way to set how strong the light is is via the intensity attribute. This is measured in lumens.

var aLight:SCNLight = SCNLight();
aLight.intensity = 100; // 100 lumens

That’s all for now.

Oscar